JPH05266718A - Electric apparatus using low thermal expansion polyimide - Google Patents

Abstract

PURPOSE:To prevent the cracking or separation of an insulating element even in heating cycles by using low thermal expansion polyimide of specific additional hardening polyimide for an insulating layer in an electric apparatus. CONSTITUTION:Low thermal expansion polyimide which is formed of additional hardening polyamide as shown in Formula I, II, or III (-X is as shown in Formula IV, -R<1-6> is -H meaning lower alkyl, aralkyl or aryl, -R<7> is -H meaning lower alkyl or aryl, and n is 1 through 3) with the thermal expansion coefficient of hardened material being (0.7 through 3) X10<-5>K<-1> is used for an insulating layer. In this way, deformation, cracking, separation, breakage, etc., are prevented from being generated due to thermal stress caused by the difference from the thermal expansion coefficient of ceramics or metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric device using a low thermal expansion polyimide made of an addition-curable polyimide as an electric insulating layer.

[0002]

2. Description of the Related Art Almost all organic polymers have a coefficient of thermal expansion (linear expansion coefficient) of 4 × 10 to ⁵ K to ¹ or more in the temperature range below the glass transition temperature, and metal or inorganic substances (Si:
0.8 × 10 ~ ⁵ K ~ ¹ , Al: 2 × 10 ~ ⁵ K ~ ¹ , Cu: 1.
8 × 10 to ⁵ K to ¹ , Ag: 2.0 × 10 to ⁵ K to ¹ ), which is a much larger value. Therefore, when these are integrated with the organic polymer, thermal stress is generated due to the difference in thermal expansion coefficient, and deformation, cracks, peeling, breakage, and the like occur.

For example, when a coating film is formed on a silicon wafer as a protection film for LSI and IC, the wafer is warped, and photolithography for patterning cannot be performed, or the resolution is extremely deteriorated. When the stress is large, the passivation film as the wiring protection film may be peeled off or the silicon wafer itself may be cleaved. Therefore, Japanese Patent Laid-Open No. Sho 60
As disclosed in Japanese Patent Laid-Open No. 32827/1992, a polycondensation type polyimide having an extremely small thermal expansion coefficient equivalent to that of a metal or an inorganic substance has been proposed.

In the three-dimensional circuit element corresponding to the high density and the high function of the MOS type LSI, when the unevenness of the surface of the semiconductor element substrate is flattened to draw a fine pattern, water or the like is used at the time of hardening. Proposal of use of addition-polymerization type polyimide, which is less likely to cause swelling or the like on the substrate surface because low-molecular volatile components are not generated (JP-A-56-90834, etc.)
Has been done.

[0005]

Although the polycondensation type polyimide has a small coefficient of thermal expansion, it generates a low molecular volatile component such as water during curing, and when applied to an insulating substrate such as LSI,
There is a problem that the surface is likely to be swollen and the flatness of the coating film is poor.

Further, the above-mentioned addition polymerization type polyimide has a large thermal expansion coefficient of 4 × 10 to ⁵ K to ¹ , so that an inorganic substance (ceramic: 0.3 × 10 to ⁵ K to ^1, etc.) or a metal (aluminum: 2).
× 10 ~ ⁵ K ~ ^1, copper: 1.8 × 10 ~ ⁵ K ~ deformed by thermal stress due to a difference in thermal expansion coefficient between ¹ etc.), cracking, peeling,
There was a problem that destruction and the like would occur.

Industrial laminated boards such as those for computers tend to have higher density and higher integration. Along with this, it is required to develop an addition polymerization type polymer having excellent heat resistance, high dimensional stability, and good through hole reliability. Conventionally, an amino bismaleimide-based material disclosed in JP-B-46-23250 and the like, an epoxy-modified resin proposed in JP-A-56-29909 and the like have been used. However, the thermal expansion coefficient of these addition-polymerization type polymers is 4 × 10.
~ ⁵ K ~ ¹ or more, so it is misaligned due to thermal expansion or contraction, or is deformed, cracked, peeled or broken due to thermal stress based on the difference between the thermal expansion coefficient of low thermal expansion ceramics or metals such as copper. There was a problem that was caused.

An object of the present invention is to provide an electric device using an addition type low thermal expansion polyimide which can solve the above problems as an electric insulating layer.

[0009]

The above objects are achieved by developing an addition cure type low thermal expansion polymer. An enormous number of addition-curable heat-resistant materials are known, including bismaleimide disclosed in Japanese Patent Publication No. 44-20625, etc., but an example of systematically examining the relationship between the chemical structure and the coefficient of thermal expansion is I can't find it. In view of such circumstances, the present inventors have made many synthetic experiments on addition-curable polyimides and studied in detail the relationship between the raw material components and the coefficient of thermal expansion. As a result, they have found that the specific addition-curable polyimide has a small coefficient of thermal expansion.

The addition-curable polyimide used in the present invention is
The coefficient of thermal expansion of the cured product is (0.7 to ³ ) × 10 to ⁵ K to ¹
The low thermal expansion polyimide is represented by the following general formula [1], [2] or [3].

[0011]

[Chemical 2]

The addition curing type polyimide used in the present invention is used as a varnish for (1) insulating thin film for semiconductor, (2) copper clad laminate, (3) flexible printed circuit board, (4) solar cell substrate, and (5). It is very useful because it can be applied to high-density module substrate, (6) heat insulating film for liquid crystal / FAX head, (7) substrate for magnetic tape / magnetic disk, (8) liquid crystal alignment film, (9) coil insulation, etc. .. Some specific examples will be described with reference to FIGS.

FIG. 1 shows a cross section of a multi-layer wiring part of an LSI.
1 is a silicon wafer, 2 is a thermal oxide film, 3 is Al wiring, 4
Is an insulating film made of the low thermal expansion polyimide film of the present invention, and 5 is an inorganic protective film.

The low thermal expansion polyimide film 4 maintains the characteristic of an organic material that a flat wiring structure can be formed, and has a low thermal expansion. Therefore, for example, an inorganic protective film 5 having a low thermal expansion such as a SiO ₂ film which is excellent as a moisture-proof film can be formed on the polyimide film 4 having a low thermal expansion, and a crack or peeling is caused due to a small difference in thermal expansion coefficient between the two. Does not occur, and the effect of moisture resistance protection is not impaired.
On the other hand, the conventional LSI cannot form the inorganic protective film 5 and requires high moisture resistance reliability.
Couldn't get

FIG. 2 is a sectional view of a memory element having an α-ray shielding film, 6 is a wiring layer, and 7 is a lead wire. When the low thermal expansion polyimide 4 of the present invention is used as the α-ray shielding film, the difference in thermal expansion coefficient between the silicon wafer 1 and the wiring layer 6 is small, and thus cracks due to thermal stress which are a problem when using a conventional polymer. The peeling does not occur, and the wafer is not bent and the resolution of the patterning of the photoresist is not lowered.

FIG. 3 shows a cross section of the magnetic disk.
Is a magnetic thin film formed by sputtering or the like, and 9 is a protective film. By adopting the low thermal expansion polyimide 4 of the present invention, cracks are not generated in the magnetic thin film 8 and the protective film due to distortion due to temperature fluctuation, disturbance of recorded signals or thermal stress.

FIG. 4 is a partially exploded perspective view of a multi-chip module using a high-density wiring substrate formed on an alumina substrate, 10 is an alumina substrate, 11 is a lead pin, and 12 is a lead pin.
Is an LSI formed by face-down bonding, 13
Is a solder ball for bonding, and 14 is a discrete wire. When a polymer having a large coefficient of thermal expansion is used for the interlayer insulating film, internal stress of the insulating film, disconnection of the wiring 3, bending of the substrate 10, cracks, Peeling etc. occurs.

By using the low thermal expansion polyimide of the present invention for the insulating layer, it is possible to obtain a multilayer wiring board which does not cause the above-mentioned abnormality even when 30 or more layers are laminated.

FIG. 5 is a sectional view of a printed wiring board based on an LSI-mounted metal plate, 15 is a metal substrate, 16 is an LSI chip manufactured by a film carrier method, 17 is a carrier film using low thermal expansion polyimide, and 18 is It is a terminal.

Low thermal expansion polyimide carrier film 1
High-precision and high-density LSI chip 16 for use as
Is obtained. Further, since the stress applied to the bonding solder ball 13 can be greatly reduced, fatigue fracture is reduced. Further, by using the low thermal expansion polyimide of the present invention for the insulating film 4 of the wiring portion 3 formed on the metal substrate 15, a printed wiring board without bending can be obtained, and high-precision high-density mounting can be performed.

FIG. 6 is a sectional view of a metal substrate module mounted by the lead wire bonding method. 1
Reference numeral 9 denotes a lead wire bonding type LSI chip.

When the film is used as an insulating film for a film insulating coil fixed with a solventless epoxy impregnated varnish, the difference in the coefficient of thermal expansion between the coil material such as copper or aluminum and the insulating film is small, so that cracks in the insulating layer occur. It is possible to prevent the peeling and the reduction of the insulation resistance and the dielectric breakdown voltage due to the peeling.

When a metal foil such as stainless steel coated with a thin film of the low thermal expansion polyimide of the present invention is used as a substrate of a solar cell using amorphous silicon, cracks in the amorphous silicon thin film are reduced as compared with the case of using conventional polyimide. Occurrence can be significantly reduced.

When the low thermal expansion polyimide of the present invention is used as a film for a flexible printed board, since the coefficient of linear expansion with the metal wiring material is small, the flexible printed board is curled as in the case of using conventional polyimide. And a flat flexible printed circuit board can be obtained. Further, since it can be produced by a method of directly applying a varnish on the metal foil, the production process is halved as compared with the conventional method of laminating a metal foil and a film produced in advance with an adhesive, and It is possible to prevent deterioration of heat resistance due to the low temperature curable adhesive. Since this flexible printed board has a small coefficient of thermal expansion, when it is used as a multilayer wiring board, the positional displacement between layers is extremely small, and high-density mounting is possible.

When used as a molding material for a semiconductor device or the like, the problem of cracking or deformation of the chip does not occur.

[0026]

The addition-curable polyimide used in the present invention has an extremely small coefficient of thermal expansion equivalent to that of metals such as copper and aluminum, and inorganic materials such as ceramics and glass. The thermal stress due to is extremely small, and therefore deformation, cracks, peeling, breakage, etc. do not occur. In addition, since it is an addition-curing type that does not generate volatile components, it is possible to form a thick film without causing swelling or the like.

The reason why the addition-curable polyimide used in the present invention exhibits low thermal expansion is probably because the packing is larger than that of other polyimides.

[0028]

EXAMPLES Next, the present invention will be described in detail with reference to Examples.

Examples 1 to 6 and Comparative Examples 1 and 2 A four-necked flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet was used.
300 g of 2-pyrrolidone (NMP) was added and dissolved with stirring under a nitrogen stream. Next, maleic anhydride was added, and the mixture was stirred at about room temperature for about 1 hour. Then, acetic anhydride 300
g and 20 g of potassium acetate were added, and the mixture was stirred well to effect dehydration and ring closure. When the dehydration ring closure is difficult to proceed, heating was performed as necessary. Then, the reaction solution was poured into water, and the formed bismaleimide precipitate was filtered and dried under reduced pressure.

The obtained bismaleimide was treated at 230 ° C./1
0 minutes → 250 ° C./30 minutes → 270 ° C./30 minutes → 300 ° C.
/ 30 minutes heat curing. The obtained resin plate was heated to 350 ° C. and was cooled to release the residual strain, and then the dimensional change was measured using a thermomechanical tester (TMA) under the condition of 5 ° C./min. The linear expansion coefficient was obtained from the amount of dimensional change below the glass transition point. The glass transition temperature was 350 ° C. or higher in all cases.

[0031]

[Table 1]

Example 7 and Comparative Example 3 Each of the bismaleimides obtained in Example 1 was dissolved in N, N-dimethylformamide to prepare a varnish having a solid content of 50% by weight. Aminosilane-treated glass cloth (0.1 mm thick manufactured by Nitto Boseki Co., Ltd.) was impregnated with this varnish and the temperature was adjusted to 130 to 140 ° C. for 30 to 6 mm.
It was heated and dried for 0 minutes to prepare a prepreg having a resin content of 40 to 50% by weight. Five pieces of this are piled up, and a copper foil with a thickness of 35 μm is piled up on both sides, 180 ° C., pressure 50 kg / cm.
² , 90 minutes, and further pressure-molded under the condition of 220 ° C./180 minutes to obtain a laminated plate. The results of evaluating the characteristics are shown in Table 2. In addition, as a comparative example, the characteristics of a laminated plate made of an amino bismaleimide resin are also shown.

[0033]

[Table 2]

Example 8 Using the maleimide NMP solution (50% by weight) of Examples 1 and 4, the height was 0.9 μm ×
A silicon wafer having an aluminum pattern with a width of 5 μm was spin coated with a spin coater. 100 ° C /
Heat treatment was performed for 1 hour → 220 ° C./1 hour → 350 ° C./1 hour to form a cured film having a film thickness of 2.6 μm. The height difference on the surface of the film was ± 0.1 μm.

Further, the silicon wafer is heated to 350 ° C. ⇔ 1
When a heat resistance cycle at 50 ° C. was carried out and a crack resistance test was conducted, it was found that 10 using the maleimide of Example 4
Some cracks were generated after the completion of 0 cycle and in the case of using the maleimide of Example 1 after the completion of 80 cycles.

[0036]

In the electric device of the present invention, the low thermal expansion polyimide used as the insulating layer is cured by an addition reaction without a volatile component, and the linear expansion coefficient after curing is (0.7 to ³ ) × 10 to ⁵ K. ~ ¹
Since it has a low thermal expansion property, cracks or peeling will not occur in the insulating layer or the like even when subjected to a heat cycle.

[Brief description of drawings]

FIG. 1 is an LS having a multilayer wiring structure showing an example of the present invention.
It is sectional drawing of I.

FIG. 2 is a cross-sectional view of a memory device having an α-ray shielding film showing an example of the present invention.

FIG. 3 is a cross-sectional view of a magnetic disk showing an example of the present invention.

FIG. 4 is a partial cross-sectional perspective view of an LSI-mounted multichip module in which high-density multilayer wiring is formed on an alumina substrate showing an example of the present invention.

FIG. 5 is a film carrier type L showing an example of the present invention.
FIG. 6 is a cross-sectional view of a metal plate-based printed board on which SI is mounted.

FIG. 6 is a cross-sectional view of a metal plate-based printed circuit board on which a lead wire bonding type LSI according to an example of the present invention is mounted.

[Explanation of symbols]

1 ... Silicon wafer, 2 ... Thermal oxide film, 3 ... Aluminum wiring, 4 ... Low thermal expansion polyimide, 5 ... Inorganic protective film, 6
... wiring layer, 7 ... lead wire, 8 ... magnetic thin film, 9 ... protective film,
10 ... Alumina substrate, 11 ... Lead pin, 12 ... LSI
Chip, 13 ... Solder pole, 15 ... Metal substrate, 16 ... Film carrier type LSI, 17 ... Carrier film, 18 ... Terminal, 19 ... Lead wire bonding type L
SI.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Motoyo Wajima 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hiritsu Manufacturing Co., Ltd.

Claims (1)

[Claims] 1. An insulating layer of an electric device is represented by the general formula [1],
An electric device using a low thermal expansion polyimide, which is an addition-curable polyimide represented by [2] or [3]. [Chemical 1]